N VITRO TRYPANOCIDAL, NEMATICIDAL AND ANTIMICROBIAL ACTIVITIES OF USNEA LETHARIIFORMIS

PIÑEIRO M; MANRIQUE S; RODRIGUEZ JM; GOMEZ J; BARRERA PA; LIMA B; SOSA M; TAPIA A

San Luis

Congreso; XXXVII Reunión Científica Anual de la Sociedad de Biología de Cuyo.; 2019

Sociedad de Biología de Cuyo

Usnea lethariiformis has been cited for Argentina and Chile and is widely distributed throughout the Andean - Patagonia province. Until now there are limited reports on its chemical composition and biological activity. Dichloromethane and methanol extracts (DCME, MeOHE) from U. lethariiformiscollected in Tierra del Fuego, Argentina, was evaluated regarding their trypanocidal, nematicidal and antioxidant activities, in conjunction with the identification of bioactive metabolites. To the assessment of trypanocidal activity, 3.106 epimastigotes/mL were incubated inDiamond?s medium supplemented with 15% fetal bovine serum and hemin at 28 °C. Treatments were performed with a concentration of 50 μg/mL (dissolved in DMSO).Negative control: parasitesincubated without extract;positive control: parasitesincubated with benznidazole (5μg/mL).Aliquots of the cultures were collected at 24, 48 and 72 h, and were counted in Neubauer chamber under optical microscopy to evaluate growth. To evaluate the survival, aliquots (24 and 48 h) were stained (eosin exclusion test) and observed under optical microscopy. For nematicidal activity, 30 juveniles at the second larval stage of Meloidogyne incognita (J2) were collected and placed in Petri dishes with 10 mL of DCME and MeOHE at 0.5 % (w/v). The antioxidant properties were evaluated by 2,2-diphenyl-1-picrylhydrazyl, trolox equivalent antioxidant capacity, and ferric reducing ability of plasma assay (DPPH, TEAC and FRAP, respectively); and lipoperoxidation inhibition in erythrocytes methods. The antibacterial activity was carried out according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. DCME and MeOHE showed a strong trypanocidal and nematicidal effect and moderated antioxidant activity. The bioassay-guided fractionation by Sephadex LH 20 and silica gel column of DCME extract led to the isolation of the main bioactive compound usnic acid; their structure was characterized by 1H-NMR, 13C-NMR, and ES-MS experiments. Usnic acid showed a potent trypanocidal and nematicidal activities and antifungal activity against Cryptococcus neoformans ATCC 32264, Microsporum gypseum C 115 2000, Trichophyton rubrum C 113 2000 and Trichophyton mentagrophytes ATCC 997 (MICs between 100-200 µg/ml). Additionally Gram (+) and (-) bacteria were inhibited (MICs values 500-1000µg/ml). Authors are grateful to CICITCA-UNSJ, UNCuyo.